Oral care products such as toothpastes are routinely used by consumers as part of their oral care hygiene regimens. It is well known that oral care products can provide both therapeutic and cosmetic hygiene benefits to consumers. Therapeutic benefits include caries prevention which is typically delivered through the use of various fluoride salts; gingivitis prevention by the use of an antimicrobial agent such as triclosan, stannous fluoride, zinc citrate or essential oils; or hypersensitivity control through the use of ingredients such as strontium chloride or potassium nitrate. Cosmetic benefits provided by oral care products include the control of plaque and calculus formation, removal and prevention of tooth stain, tooth whitening, breath freshening, and overall improvements in mouth feel impression which can be broadly characterized as mouth feel aesthetics. For example, agents such as pyrophosphate salts have been used as antitartar agents and polymeric agents such as condensed phosphorylated polymers, polyphosphonates, and carboxylated polymers have been used in oral care compositions to provide benefits including tooth surface conditioning and control of tartar, staining and astringency. To illustrate further, commonly assigned U.S. Pat. No. 6,555,094 to Glandorf, et al. discloses oral care compositions comprising a stannous ion source, a fluoride ion source, and a polymeric mineral surface active agent that binds stannous, wherein the compositions provide effective antimicrobial activity for reducing plaque and gingivitis with minimal side effects of tooth staining and astringency. The compositions simultaneously provide reduction and control of supragingival calculus. Additional disclosures related to the use of polyphosphate as mineral surface active agent in oral care compositions include commonly assigned U.S. Pat. No. 5,939,052; U.S. Pat. No. 6,187,295; U.S. Pat. No. 6,350,436; and U.S. Pat. No. 6,190,644.
The present inventors have surprisingly discovered additional important benefits of oral care compositions comprising such polymeric agents that also have affinity for the tooth surface. These polymeric agents are believed to bind to the tooth surface or form compounds or complexes on the tooth surface, thereby forming a protective film or coating thereon. As a result of these protective coatings, tooth surfaces are provided with remarkable resistance and protection against erosion caused by the action of chemicals, such as harsh abrasives and acids, as disclosed in commonly assigned copending application U.S. Ser. No. 10/319,108 published as US 2003/0165442. Included among such polymeric agents are phosphonate containing structures, particularly those containing diphosphonate groups. Examples of suitable phosphonate containing polymers are disclosed in U.S. Pat. No. 5,011,913 to Benedict et al.; U.S. Pat. No. 4,877,603 to Degenhardt et al; U.S. Pat. No. 5,980,776 to Zakikhani et al; U.S. Pat. No. 6,071,434 to Davis et al; U.S. Pat. No. 5,296,214 to Gaffar, U.S. Pat. No. 4,749,758 to Dursch et al. and GB 1,290,724 assigned to Farbwerke Hoechst.
In addition to the anticalculus and antierosion benefits of these phosphonate containing polymers, the present inventors have discovered that oral care compositions containing these polymers in combination with a fluoride ion source provide surprisingly enhanced fluoride uptake and remineralization of teeth, thereby providing enhanced protection of teeth against caries and cavities and increased resistance to acid demineralization associated with caries processes. In particular, tooth surfaces and most particularly carious lesions treated with combinations of a fluoride ion source and phosphonate containing polymers show increased surface as well as internal acquisition of mineralized forms of calcium phosphate—acquired from supersaturated solutions—thus resulting in increased remineralization. Teeth treated with such combinations moreover exhibit increased resistance to demineralization and increases in fluoridation as a component of remineralized enamel.
The superior efficacy of combinations of polyphosphonates or phosphonate containing polymers with fluoride in promoting fluoridation, remineralization and providing acid resistance to the teeth is completely unexpected by known principles of phosphonate containing agents functioning as antitartar agents. These phosphonate ingredients, like other tartar control agents, are known to be effective in reducing (rather than increasing) the crystallization of mineral salts onto substrates in supersaturated solution. The localization of these materials on tooth surfaces can be expected to assist in tartar prevention and even do this without inhibiting remineralization processes below the tooth surface. However, the ability to modify the tooth surface to promote remineralization beneath the tooth surface such as in caries prevention is completely unexpected.
The tooth caries process is the result of calcium phosphate mineral loss from tooth substrate induced by localized plaque microbiological acid production from fermentable dietary substrates. If left uninhibited, the caries process results in sufficient mineral loss from teeth, which manifests as a loss of structural integrity and the formation of a cavity. (G. H. Nancollas, “Kinetics of de- and remineralization,” pp 113-128; A. Thylstrup, J. D. B. Featherstone and L. Fredebo, “Surface morphology and dynamics of early enamel caries development,” pp 165-184 in: Demineralisation and Remineralisation of the Teeth, IRL Press Ltd., (1983). S. A. Leach and W. M. Edgar, editors). The caries process is not continuous but is described by cyclic periods of mineral loss from teeth—particularly following ingestion of fermentable carbohydrates, followed by periods of no mineral loss or even mineral repair of damaged local regions. Remineralization refers to the process of repair of acid damaged tooth structure—by the recrystallization of mineral salts on the tooth architecture. Remineralization processes are a natural protective feature of saliva against the formation of tooth cavities, as saliva is supersaturated with respect to calcium phosphate tooth mineral salts. Remineralization is accelerated by fluoride ions in solution which increase local supersaturation with respect to fluoridated calcium phosphate deposition. Fluoridation refers to the acquisition of fluoride into tooth substrates resulting from topical treatments with fluoride agents. Often, but not always, remineralized teeth from treatments exhibit increases in fluoride uptake and retention. Demineralization is the process of mineral loss from teeth caused by plaque acids or dietary acids. Demineralization can occur on tooth surfaces or below tooth surfaces depending upon the composition of the acids, concentration and pH. Morevover the teeth with increased remineralization and fluoride uptake and retention also exhibit superior resistance to acid demineralization. The processes of fluoride incorporation into teeth, remineralization and resistance to demineralization represent primary mechanisms toward the reduction of tooth decay or other acid insults. The clinical relevance of the beneficial effects of these phosphonate containing polymer and fluoride combinations is that enhancements in fluoridation, remineralization and demineralization resistance match those of topical treatments, in particular elevated doses of fluorides, proven sufficient to provide clinical enhancements in caries prevention. (K. H. Lu et al.: “A three year clinical comparison of a sodium monofluorophosphate dentifrice with sodium fluoride dentifrices on dental caries in children.” J Dent Child. 1987;54:241-244) Benefits are further validated by improved resistance to cavity formation provided by these fluoride ion source/phosphonate polymer combinations in biological tests of anticaries efficacy such as those recommended in the FDA's Final Caries Monograph for OTC dentifrice products (specifically Test Method 37).